. Obstetrics for nurses. for it to rotate to ,it must pass through anarc of 135° instead of45°. This greater rota-tion may slightly prolongthe second stage of labor,but otherwise is of nopractical , internal rota-tion occurs when thehead reaches the perin-eum, but occasionally itis delayed until the scalpis in sight, when the whole process is visible. In about ten per cent of the cases, the occiput rotates posteriorlythrough an arc of 45° and comes to occupy the hollow of the sacrum. In such cases, spon- taneous delivery isusual, but the head isborn by a differentmechanis
. Obstetrics for nurses. for it to rotate to ,it must pass through anarc of 135° instead of45°. This greater rota-tion may slightly prolongthe second stage of labor,but otherwise is of nopractical , internal rota-tion occurs when thehead reaches the perin-eum, but occasionally itis delayed until the scalpis in sight, when the whole process is visible. In about ten per cent of the cases, the occiput rotates posteriorlythrough an arc of 45° and comes to occupy the hollow of the sacrum. In such cases, spon- taneous delivery isusual, but the head isborn by a differentmechanism. Flexionpersists, and is evenexaggerated, until theocciput is pushed overthe perineum, then bya movement of exten-sion it drops back to-ward the anus, whilethe brow, nose, mouthand chin successivelyemerge beneath thesymphysis. The re-mainder of the birth proceeds in the usual manner. Occiput posterior positions are viewed with apprehension by manyphysicians, l)ut do not deserve the importance given them. The average. Fig. 65. -The occiput rotated into the hollow of thesacrum. (Williams.) THE MECHANISM OF LABOR 121 duration of labor is possibly slightly increased, but a spontaneous out-come is the rule, if the physician recognizes the condition and waitspatiently for internal rotation to occur. With _ intelligent and conservative handling the ma-ternal mortality is not increased over thatnoted in the anterior varieties, while the fetaldeath rate is scarcely appreciably higher. Changes in the Shape of the Head.—In ver-tex presentations, the prolonged pressureagainst resistance, which marks the passage ofthe head through the pelvis, results in definiteand characteristic changes in the cranium. Asthe skull bones are only united by fibrous tissueat the various sutures and fontanelles, consider-able motion is possible. Lateral pressure ex-erted by the walls of the birth canal compressesthe head and tends to cause the various bones to overlap at the sutures. This molding, as it
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectobstetrics, bookyear1
